Nonmetallic Cable Rack Arms for Corrosion-Prone Underground Vaults
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Solution Overview
Problem
Existing cable supports in underground manholes, vaults, and tunnels made of galvanized steel are prone to corrosion due to galvanic and stray current corrosion, leading to premature failure and safety hazards, as they cannot withstand the harsh underground environment effectively.
Innovation Solution
The development of cable rack arms made from non-metallic materials, such as plastic reinforced with glass or carbon fibers, which are molded to include features like acute and obtuse angles, web connections, and interfaces for mounting on various stanchions, allowing for upward rotation and reducing stress concentrations, thus enhancing durability and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If galvanized steel cable supports are used, then initial strength and structural integrity are achieved, but corrosion resistance deteriorates due to galvanic and stray current corrosion in harsh underground environments
Solution Approach 1:
The cable support structure combines non-metallic corrosion-resistant material (polymer matrix) with metallic structural components (steel arms and posts), creating a composite system where each material performs its optimal function: the polymer provides corrosion resistance while the steel provides structural strength
2Ease of manufacture
If steel stampings and weldments are used to manufacture cable supports, then manufacturing capability and structural strength are improved, but vulnerability to galvanic and stray current corrosion increases
Solution Approach 1:
The invention uses a hybrid construction combining conventional steel components (arms, posts) with a non-metallic polymer matrix, maintaining ease of manufacturing through established steel fabrication techniques while adding corrosion protection through the polymer encapsulation
3Reliability
If hot dip galvanization is applied to steel cable supports, then short-term corrosion protection is achieved, but the galvanizing coating is eventually consumed and steel oxidizes or corrodes away
Solution Approach 1:
The polymer matrix encapsulates the steel structural components, providing a continuous non-metallic barrier that protects against both atmospheric corrosion and electrochemical degradation (galvanic and stray current corrosion), extending service life beyond the limitations of galvanization
Solution Approach 2:
The design accepts that the polymer matrix may degrade over time, allowing for replacement of the entire assembly as a cost-effective solution rather than attempting to maintain corroded steel components
4Strength
If cable racks are mounted to walls with penetrations for bolts and fasteners, then structural support and stability are achieved, but stress concentrations increase in harsh environments
Solution Approach 1:
The polymer matrix acts as a flexible encapsulating shell that distributes mechanical stresses around penetration points, reducing stress concentrations at critical locations where bolts and fasteners penetrate the structure
Data Source
AI summary
A cable rack arm and support system suitable for underground power and communication service is made from a non-metallic polymer that will not rust or corrode. The cable rack arm is adapted for mounting to existing underground stanchions or for stanchions of a more modern design. Each cable rack arm is securely mounted to the stanchion. Each cable rack arm then supports one or more cables in cable rests or saddles molded atop the arm, thus keeping the cables accessibly organized in a manhole, tunnel or vault. Plastic cable ties may be used to secure the cables to the cable rack arms. Nonmetallic pins may also be used to secure the cable rack arms to the stanchions. The stanchions may be made of nonmetallic composite material that includes a fiberglass cross-layered knitted apertured mat for increased strength.